FastAPI is a high-performance web framework for building APIs with Python.

Key Features * High Performance: Built on top of Starlette (for web routing) and Pydantic (for data validation), making it one of the fastest Python frameworks available—on par with NodeJS and Go. * Native Async Support: Full asynchronous capability out-of-the-box using standard Python async and await syntax via ASGI servers like Uvicorn. * Automatic Interactive Documentation: Generates OpenAPI-compliant web documentation (Swagger UI at /docs and ReDoc at /redoc) directly from your code parameters. * Data Validation & Type Safety: Automatically validates HTTP request body data, query parameters, and headers using Pydantic schemas, reducing runtime bugs. * Developer Ergonomics: Provides excellent code autocompletion and type-checking support in IDEs (like VS Code and PyCharm). Minimal Code Example from fastapi import FastAPI from pydantic import BaseModel app = FastAPI() # Data schema using Pydantic class Item(BaseModel): name: str price: float is_offer: bool = None # GET Endpoint @app.get("/") def read_root(): return {"message": "Hello, FastAPI"} # POST Endpoint with automatic payload validation @app.post("/items/") def create_item(item: Item): return {"item_name": item.name, "total_price": item.price * 1.1} When to Use FastAPI * Microservices & REST APIs: Ideal for lightweight, scalable backend systems. * Data Science & ML Deployment: Commonly used to expose machine learning models as production endpoints due to its fast JSON serialization and low overhead. * Asynchronous Pipelines: When your API handles heavy concurrent I/O operations, such as external API calls or database reads.